Location continuity service for locating mobile devices using multiple access networks including wireless telecommunication networks

ABSTRACT

A location continuity service having a location continuity application server (“LCAS”) that utilizes location data generated by multiple networks to determine the location of a mobile device is disclosed. The LCAS specifies a suitable reconciliation process that identifies two or more location estimation techniques that are implemented by different access networks and indicates how to utilize the location data produced by the identified estimation techniques. The LCAS interacts with various access networks identified by the reconciliation process in order to receive location data (e.g., positioning measurements and/or estimated locations) generated by the access networks and analyzes the received data to determine the location of a mobile device and provide the determined location to a location-based service. In some examples, an LCAS also provides location continuity when a mobile device moves between a home communications system and a visited communications system.

BACKGROUND

The popularity of location-based services has substantially increased inrecent years. For example, mobile device users now employ location-basedservices for navigation, to perform location-based searching, to receivelocation-based alerts or advertising, to search for or receivenotification of nearby acquaintances, and/or the like. Likewise, otherparties (e.g., network operators, third-party location-based serviceproviders, remote telemetry users, advertisers, etc.) may employlocation-based services to enable emergency services (e.g., E911services), enable asset tracking or recovery services, providelocation-based alerts or advertising, provide notification of nearbyacquaintances, perform network registration or billing, and/or the like.The recent increase in the popularity of location-based services has ledto the development of many different location determination techniquesfor mobile devices. Certain location determination techniques may besuitable only for certain kinds of mobile devices and/or certain kindsof radio access networks.

Many different types of radio access networks have been deployed tofacilitate radio transmissions to and from mobile devices. As a result,at a single geographic location, a mobile device user may be able toconnect to more than one type of radio access network. For example,standing on a street corner, a mobile device user may be able to connectsimultaneously to a Global System for Mobile Communications (“GSM”)network and a Worldwide Interoperability for Microwave Access (“WiMAX”)network. In addition, at any single geographic location a mobile deviceuser may be able to access a hard-wired access network, such as a cablenetwork or a landline phone network. Thus, at a certain time point, amobile device may be located by more than one location determinationtechnique using one or more wired or wireless access networks. Forexample, at a particular time, a mobile device may be located by atechnique suitable for GSM networks (e.g., Uplink Time Difference ofArrival (“U-TDOA”) techniques) and a technique suitable for WiMAXnetworks (e.g., Assisted Global Positioning System (“AGPS”) techniques).

As a mobile device user moves, the types of available access networksmay also change. For example, during the first part of a session, whichmay include a voice, data, multimedia, location and/or messagingsession, a mobile device may only be in range of a GSM network but afterits user moves, the device may only be able to access a WiMAX network.Thus, during a single session (e.g., a single voice call) on a mobiledevice, the location determination techniques available to locate thatmobile device may change.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a representative environment in which a locationcontinuity service operates.

FIG. 2 is a diagram illustrating an example use case where positioncontinuity and location continuity are maintained across networks andmobile devices by the location continuity service during a session.

FIG. 3 is a block diagram of a suitable communications system in whichthe location continuity service operates.

FIG. 4 is a block diagram of a location continuity application server.

FIG. 5 shows a table that conceptually illustrates how a locationcontinuity application server stores location data.

FIG. 6 is a logical flow diagram of a process for initiating andutilizing multiple location estimations in one or more access networks.

FIG. 7A is a logical flow diagram of a process for providing improvedlocation continuity when a mobile device roams from a home accessnetwork to a visited access network.

FIG. 7B is a logical flow diagram of a process for determining thelocation of a mobile device when the device roams from a home accessnetwork to a visited access network.

FIG. 8 is a logical flow diagram of a process for determining thelocation of a mobile device when a device roaming in a visited accessnetwork returns to a home access network.

DETAILED DESCRIPTION

Described herein is a location continuity service having a locationcontinuity application server (“LCAS”) that utilizes location datagenerated by multiple access networks, to determine the location of amobile device. Responsive to a service request for a location of amobile device, the LCAS specifies a suitable reconciliation process thatidentifies two or more location estimation techniques that areimplemented by different access networks and indicates how to utilizethe location data produced by two or more identified estimationtechniques. In accordance with the applied reconciliation process, theLCAS interacts with various access networks identified by the process inorder to receive location data generated by the access networks,including positioning measurements and/or estimated locations. The LCASanalyzes the received location data to determine the location of amobile device and provide the determined location to a location-basedservice.

In some examples, an LCAS also provides improved location continuitywhen a mobile device moves between a home communications system and avisited communications system. In one example, when a mobile devicemoves from a home communications system to a visited communicationssystem, a home LCAS associated with the home communications systemprovides determined location information to a visited LCAS associatedwith the visited communications system. In another example, when amobile device moves from a visited communications system to a homecommunications system, a home LCAS requests and receives determinedlocation information from a visited LCAS.

Typical location estimation or determination techniques implemented byradio access networks include Time Difference on Arrival (“TDOA”)(including Uplink-TDOA (U-TDOA), Observed TDOA (“OTDOA”), Ideal PeriodDownlink-OTDOA (“IPDL-OTDOA”), and other TDOA procedures), CellIdentification (“CI”), CI plus Timing Advance (“CI-TA”), use of a GlobalPositioning System (“GPS”), use of an Assisted Global Positioning System(“AGPS”), Assisted Global Navigation Satellite System (“AGNSS”), RoundTrip Time (“RTT”) measurements, CI plus RTT (“CI-RTT”), EnhancedObserved Time Difference (“E-OTD”), WiFI Data Base location,triangulation, and/or the like. Some of these location estimationtechniques determine or estimate the location of a mobile device usingavailable information, such as an identifier of a cell, femtocell,picocell, access point, base station, Node-B, eNode-B, cell site, and/orother network component or network that is accessible to the mobiledevice. Suitable identifiers include an Internet Protocol (“IP”)address, a Cell Global Identity (“CGI”), an Enhanced CGI (“E-CGI”), aMedia Access Control (“MAC”) address, a Service Set Identifier (“SSID”),an International Mobile Subscriber Identity (“IMSI”), an InternationalMobile Equipment Identity (“IMEI”), a serial number, and/or the like.Suitable examples of determining or estimating the location of a mobiledevice according to an identifier or other technique are described inInternational Patent Application PCT/US2007/066579, entitled “MobileComputing Device Geographical Location Determination,” which was filedon Apr. 12, 2007; International Patent Application PCT/US2006/041226,entitled “System and Method for Determining Device Location in anIP-Based Wireless Telecommunications System,” which was filed on Oct.20, 2006; International Patent Application PCT/US2007/082136, entitled“System and Method for Utilizing IP-Based Wireless TelecommunicationsClient Location Data,” which was filed on Oct. 22, 2006; andInternational Patent Application PCT/US2007/082133, entitled “Two StageMobile Device Geographical Location Determination,” which was filed onOct. 22, 2006; all of which are hereby incorporated by reference intheir entirety.

A location continuity service having an LCAS may be employed tofacilitate the provisioning of location-based services to mobile deviceusers, emergency services users, network operators, remote telemetryusers, and others. The use of an LCAS enables service providers toprovide better position continuity and location continuity as a mobiledevice utilizes various access networks to improve the overall end-userexperience and to provide a rich communication service to an end-user.An LCAS may also permit service providers to locate a mobile device moreaccurately and/or more quickly while utilizing fewer system resourcesand/or incurring lower costs.

Various embodiments of the invention will now be described. Thefollowing description provides specific details for a thoroughunderstanding and an enabling description of these embodiments. Oneskilled in the art will understand, however, that the invention may bepracticed without many of these details. Additionally, some well-knownstructures or functions may not be shown or described in detail, so asto avoid unnecessarily obscuring the relevant description of the variousembodiments. The terminology used in the description presented below isintended to be interpreted in its broadest reasonable manner, eventhough it is being used in conjunction with a detailed description ofcertain specific embodiments of the invention.

Illustrative Environments

FIG. 1 illustrates a representative environment 100 in which thelocation continuity service may operate. Environment 100 includes mobiledevices 110, 112, and 114 and wireless or wired networks 120, 122, 124,and 130. Mobile devices 110, 112, and 114 are configured to communicatewith, or through, one or more of networks 120, 122, 124, and 130.Although mobile devices by their nature will typically connect via awireless network, under certain circumstances mobile devices may connectvia a wired network.

Mobile devices 110, 112, and 114 may include virtually any devices forcommunicating over a wireless network. Such devices include mobiletelephones, such as Global System for Mobile Communications (“GSM”)telephones, Time Division Multiple Access (“TDMA”) telephones, UniversalMobile Telecommunications System (“UMTS”) telephones, Evolution-DataOptimized (“EVDO”) telephones, Long Term Evolution (“LTE”) telephones,Generic Access Network (“GAN”) telephones, Unlicensed Mobile Access(“UMA”) telephones, and other mobile computers or devices, such as Voiceover Internet Protocol (“VoIP”) devices, Secure User Plane Location(“SUPL”) Enabled Terminals (SETs), Personal Digital Assistants (PDAs),radio frequency devices, infrared devices, handheld computers, laptopcomputers, wearable computers, tablet computers, pagers, integrateddevices combining one or more of the preceding devices, and/or the like.As such, mobile devices 110, 112, and 114 may range widely in terms ofcapabilities and features. For example, a mobile telephone may have anumeric keypad, the capability to display only a few lines of text andbe configured to interoperate with only GSM networks. However, othermobile devices (e.g., smart phones) may have a touch-sensitive screen, astylus, an embedded GPS receiver, and a relatively high-resolutiondisplay and be configured to interoperate with multiple types ofnetworks. Mobile devices 110, 112, and 114 may also include SIM-lessdevices (i.e., mobile devices that do not contain a functionalsubscriber identity module (“SIM”)), roaming mobile devices (i.e.,mobile devices operating outside of their home access networks), and/ormobile software applications.

Users may employ mobile devices 110, 112, and 114 to communicate withother users or devices. In addition, users may employ mobile devices110, 112, and 114 to receive, provide, or otherwise interact withlocation-based services such as emergency services (e.g., E911), assettracking or recovery services, location-based alerts or advertisingservices, social networking services such as identification of nearbyfriends and family, and/or the like. Additionally, network operators mayutilize location-based services to perform network registration of amobile device 110, 112, 114 or billing/charging for mobile deviceservices. Location-based services may be initiated via networkcomponents or via the mobile device.

Mobile devices 110, 112, and 114 typically include a processing unit,volatile memory and/or nonvolatile memory, a power supply, one or morenetwork interfaces, an audio interface, a display, a keypad or keyboard,a GPS receiver and/or other location determination component, and otherinput and/or output interfaces. The various components of mobile devices110, 112, and 114 may be interconnected via a bus. The volatile andnonvolatile memories generally include storage media for storinginformation such as processor-readable instructions, data structures,program modules, or other data. Some examples of information that may bestored include basic input/output systems (BIOS), operating systems, andapplications. In addition, the memories may be employed to storeoperational data, content, contexts, and/or the like. The memories mayalso store one or more applications configured to receive and/or providemessages to and/or from another device or component. These messages mayalso be displayed and/or stored on mobile device 110, 112, or 114. Suchmessages may include short message service (SMS) messages, multi-mediamessage service (MMS) messages, instant messaging (IM) messages,enhanced message service (EMS) messages, rich communication servicecontent, and/or any other content directed toward a user of mobiledevices 110, 112, or 114. The memories of mobile devices 110, 112, and114 may also store one or more applications configured to receive and/orprovide information to location-based services, or to facilitateperformance of location estimation or determination techniques. Thememories may also store applications for performing location estimationor determination techniques.

Networks 120, 122, 124, and 130 may include virtually any radio accessnetworks or hard-wired access networks (collectively, “access networks”)for facilitating communications to or from mobile devices 110, 112, and114 using any wireless protocol or standard. These protocols orstandards include GSM, TDMA, UMTS, EVDO, LTE, GAN, UMA, Code DivisionMultiple Access (“CDMA”) protocols (including IS-95, IS-2000, and IS-856protocols), Advanced LTE or LTE+, Orthogonal Frequency Division MultipleAccess (“OFDM”), General Packet Radio Service (“GPRS”), Enhanced DataGSM Environment (“EDGE”), Advanced Mobile Phone System (“AMPS”), WiMAXprotocols (including IEEE 802.16e-2005 and IEEE 802.16m protocols),Wireless Fidelity (“WiFi”), High Speed Packet Access (“HSPA”),(including High Speed Downlink Packet Access (“HSDPA”) and High SpeedUplink Packet Access (“HSUPA”)), Ultra Mobile Broadband (“UMB”), VoIP,SUPL, IP Multimedia Subsystem (“IMS”), and/or the like. Additionally,networks 120, 122, 124, and 130 may include hard-wired networks forfacilitating communications to or from mobile devices 110, 112, and 114using any protocol or standard, such as cable networks, wired telephonenetworks (e.g., a PSTN), or other wired IP networks. Networks 120, 122,124, and 130 may be operated by a mobile telephony service provider, acable operator, an Internet service provider, online service providers,a wired telephone network operator or service provider, businesses,individuals, or other network operators.

In FIG. 1, networks 120, 122, and 124 are illustrated as macronetworks,e.g., networks typically designed to cover relatively large areas suchas cities, metropolitan areas, regional areas, multistate areas, and/orthe like. Protocols and standards such as GSM, TDMA, UMTS, EVDO, LTE,CDMA, OFDM, GPRS, EDGE, AMPS, WiMAX, UMB, and/or the like are generallyemployed with macronetworks. Further, network 130 is illustrated as amicronetwork, e.g., a network typically designed to cover a smaller areasuch as a neighborhood, park, city, building, home, and/or the like. Toprovide an example, protocols and standards such as WiFi, GAN, UMA,Wireless Universal Serial Bus (WUSB), ZigBee, and/or the like aregenerally employed with micronetworks. However, in certain circumstances(e.g., in conjunction with picocell broadcast architecture or the like),micronetworks may also employ protocols or standards more traditionallyassociated with macronetworks. For example, in some implementations, LTEor 3G protocols may be used in a micronetwork that provides typicalLTE/3G functionalities but over a smaller physical range than typicalLTE/3G networks. Such networks or their components may be known as anano-e-node Bs or home e-node Bs (“HeNB”).

At any given location, one or more of networks 120, 122, 124, and 130may provide overlapping coverage areas. For example, at a particulargeographical location, a mobile device 110, 112, 114 may be within rangeof a UMA network, a GSM network, a UMTS network, an EVDO network and maybe physically connected to a hard-wired IP-based cable network. Atanother geographical location, the mobile device may be within range ofthe same set or a different set of networks.

At times, a user of a mobile device 110, 112, 114 or a party providingservices to a mobile device may want to determine the location of themobile device. To improve the performance of a location determination,it may be advantageous to utilize more than one overlapping network todetermine the location of the mobile device. Described herein is alocation continuity application server (“LCAS”) that utilizespositioning measurements and/or estimated locations that are generatedby multiple networks. The LCAS applies a reconciliation process thatidentifies two or more location estimation techniques that areimplemented by different access networks and indicates how to utilizethe two or more identified estimation techniques. In accordance with thereconciliation process, the LCAS interacts with various access networksidentified by the process in order to receive location data orinformation from the access networks, including positioning measurements(i.e., data that can be used to estimate a device location) and/orestimated locations (i.e., estimates of a device location). The LCASalso analyzes the received location data to determine the location of amobile device and provide the determined location to a location-basedservice.

To improve the performance of a location-based service, it is desirableto maintain position continuity and location continuity across asession. One intuitive example of a session is a telephone voice callmade using a particular mobile device. In such an example, positioncontinuity refers to taking continuous positioning measurements of themobile device within a network (e.g., continuously making RTTmeasurements or range measurements) during the session, even as themobile device utilizes different types of access networks at differentpoints during the call. In the example, location continuity refers tocontinuously determining or estimating the geographic location of themobile device (e.g., latitude, longitude and/or altitude) using thepositioning measurements (e.g., using RTT analysis techniques) andproviding determined locations to a location-based service even as themobile device utilizes different access networks or moves away from oneof the home access networks. Other examples of sessions include data,multimedia, location and/or messaging sessions.

In other scenarios, a session may span multiple access networks, mobiledevices, IMSs, network cores, applications running on mobile devices orelsewhere, application sessions, charging schemes (i.e., billingschemes), or other session factors. Generally speaking, positioncontinuity refers to the ability to continuously take positioningmeasurements of one or more mobile devices 110, 112, and 114 usingnetwork hardware such as one or more SMLC, SAS, E-SMLC, SPC, LIS, and/orIP SMLC (all described herein with respect to location estimationcomponent 350) even as one or more session factors change during asession (e.g., as the access network, application, or mobile device thatis used changes). Location continuity generally refers to preserving theability to deliver an initial location estimate and subsequent updatedlocation estimates to a public safety answering point (“PSAP”) oranother location-based service, following a handover from one accessnetwork to another (and/or following a change in another sessionfactor), in a manner that is transparent to the PSAP or location-basedservice. The definitions of a session and session continuity aredeveloped in greater detail in technical specifications and reportsdeveloped by the 3rd Generation Partnership Project (“3GPP”™), includingTR 23.893 v8.0.0, which is incorporated herein by reference in itsentirety.

FIG. 2 is a diagram illustrating an example use case where positioncontinuity and location continuity are desirable across a sessioninvolving an emergency call (e.g., a 911 call). In the depicted example,at time T1 a mobile device 110 utilized by a user is in range of a GSMaccess network 122. At time T1 the user requests and receives anestimate of his location using a navigation program installed on themobile device. At time T2, as a result of motion by the user, the mobiledevice 110 is in range of both the GSM access network 122 and a UMTSaccess network 120. At time T2, the user utilizes the mobile device toinitiate an emergency call (e.g., a 911 call to report a serious caraccident). At time T3, the mobile device 110 has moved out of range ofthe GSM access network 122 (e.g., because the user drives out of therange of the GSM access network, or because the GSM access networkotherwise becomes unavailable). Prior to time T4, the user of mobiledevice 110 adds a second mobile device 112 to the same emergency call(e.g., using three-way calling or transfer features). The mobile device110 may also hang up on the emergency call. At time T4, the secondmobile device 112 remains in range of the UMTS access network 120 but isalso in range of a GAN access network 130.

In the example depicted in FIG. 2, it is desirable to rapidly andaccurately determine the location of the mobile device 110 at theinitiation of the call so that the emergency call may be suitably routedto an appropriate PSAP or similar entity. To do so, the disclosedlocation continuity service utilizes positioning measurements andlocation estimates from two or more of the multiple telecommunicationnetworks that are accessible to the mobile device. That is, at time T1,the location continuity service may provide the positioning measurementsand/or location estimates generated by the GSM access network 122 tonetwork components to perform the emergency call routing. At time T2,the location continuity service may also take simultaneous positioningmeasurements and/or location estimates from the UMTS access network 120since the UMTS access network is also accessible to the mobile device.The positioning measurements and/or location estimates from the twonetworks may be used alone or in combination to ensure the highestlocation accuracy. Similarly, the location continuity service quicklyfixes and provides the determined location of the second mobile device112 when the second mobile device is added to the emergency call. To doso, the location continuity service may utilize the positioningmeasurements and/or location estimates already generated for the mobiledevice 110 from the UMTS network at time T3 to estimate the location ofthe second mobile device. The location continuity service may alsosupplement or supplant the positioning measurements and/or locationestimates from the mobile device 110 with positioning measurementsand/or location estimates for the second mobile device 112 from the UMTSaccess network 120 or GAN access network 130. By doing so, the locationcontinuity service provides the best location information regarding thesession to the PSAP.

Illustrative Communications System

FIG. 3 illustrates a communications system 300 in which the locationcontinuity service may be utilized to provide position and locationcontinuity across access networks. Communications system 300 depictsfive access networks 340-344 that are coupled to supporting networkinfrastructure via one or more core networks 370. While five accessnetworks are depicted in FIG. 3, it will be appreciated that a greateror lesser number of access networks may exist within the communicationssystem 300. The communications system 300 depicted in FIG. 3 is operatedby one or more telecommunications service providers, and may be coupled(not shown) with other communications systems operated by the same orother telecommunications service providers.

A second-generation radio access network (“2G RAN”) 340 may include anycombination of radio access networks that utilize second-generation(“2G”) and 2G transitional mobile telephony protocols to communicatewith mobile devices, such as radio access networks that use protocolssuch as GSM, IS-95, GPRS, IS-2000, and/or EDGE. The 2G RAN 340 may takepositioning measurements and/or provide location estimates by utilizingtechniques that are compatible with the applicable second-generationprotocols. For example, the 2G RAN 340 may comprise a GSM access networkconfigured to provide positioning measurements and/or location estimatesusing U-TDOA, CI-TA, E-CGI, GPS, AGPS, and/or E-OTD techniques and/orhybrid methods that employ combinations of these techniques.

A third-generation radio access network (“3G RAN”) 341 may include anycombination of radio access networks that utilize third-generation(“3G”) and 3G transitional mobile telephony protocols to communicatewith mobile devices, such as radio access networks that use protocolssuch as UMTS, IS-856, HSDPA, HSUPA, EVDO, and/or IEEE 802.16e-2005. Forexample, 3G RAN 341 may comprise a UMTS access network configured toprovide positioning measurements and/or location estimates using CI,CI-RTT, GPS, AGPS, and/or OTDOA techniques and/or hybrid methods thatemploy combinations of these techniques.

A fourth-generation radio access network (“4G RAN”) 342 may include anycombination of radio access networks that utilize fourth-generation(“4G”) and 4G transitional mobile telephony protocols, such as radioaccess networks that communicate with mobile devices using protocolssuch as LTE, Advanced LTE or LTE+ and WiMAX. As an example, 4G RAN 342may comprise a WiMAX access network that provides positioningmeasurements and/or location estimates using A-GPS, U-TDOA, Cell ID,and/or hybrid methods that employ combinations of these techniques. Asanother example, 4G RAN 342 may comprise an LTE access network thatprovides positioning measurements and/or location estimates using AGPS,downlink positioning, CI and enhanced CI techniques, OTDOA, TDOA, AGNSSand/or hybrid methods that employ combinations of these techniques.

An IP radio access network (“IP RAN”) 343, provides voice and/or dataaccess to mobile devices and may comprise one or more access pointsand/or Unlicensed Network Controllers (“UNCs”) that route communicationsbetween mobile devices and other network components over an IP-basednetwork. An access point typically provides coverage for a relativelysmall area, such as for a femtocell within a building (e.g., home,office, shopping mall, train station, or the like) or within anaircraft, ship, train, or other vehicle. An access point may take theform of a WiFi access point, a HotSpot component, a wireless router, awireless access point, and/or the like. As one example, IP RAN 343 maycomprise a GAN that provides location estimates using identifiers suchas MAC addresses, IMSI, IP addresses, and/or CGI and/or hybrid methodsthat employ combinations of these identifiers.

A hard-wired access network 344 provides IP-based network access tomobile devices via a wired physical communication link between themobile device and the hard-wired access network 344. For example, ahard-wired access network 344 may comprise a cable network, a publicswitched telephone network (PSTN), and/or similar. As one example, ahard-wired access network 344 may provide positioning measurementsand/or location estimates for a mobile device using the HTTP EnabledLocation Delivery (“HELD”) standards generated by the InternetEngineering Task Force (“IETF”), details of which may be found attools.ieff.org. Other wireless IP-based networks (e.g., IP RAN 343) maysimilarly provide positioning measurements and/or location estimatesusing HELD standards. As another example, a hard-wired access network344 may also provide positioning measurements and/or location estimatesfor a mobile device using a customer provided location address, an IPlocation, and a Layer 2 address of the end device.

Each of the various access networks 340-344 may be connected to alocation estimation component 350 that provides and/or coordinatespositioning measurements and/or location estimations within thecorresponding access networks 340-344. Location estimation components350 may comprise one or more discrete location estimation systemsincluding, inter alia, a Serving Mobile Location Center (“SMLC”), aStandalone Assisted GPS SMLC (“SAS”), a Location Information Server(“LIS”) (e.g., as described by the HELD standards discussed previously),and/or an IP SMLC. For simplicity, in FIG. 3, all the various discretelocation estimation systems are shown within a single, amalgamatedlocation estimation component 350, since each discrete system providessimilar or analogous functionality. However, one having skill in the artwill appreciate that a given access network may only be directlyconnected to a subset of the discrete systems represented by theamalgamated location estimation component 350. For example, a 2G RAN 340may only be directly connected to an SMLC within the location estimationcomponent 350 and not to an SAS. Moreover, certain location estimationsystems may be connected to and provide location services acrossmultiple networks 340-344. The communications system 300 may compriseother components that also provide and/or coordinate positioningmeasurements and/or location estimations within access networks, butthese additional components may not be directly connected to the variousaccess networks. For example, the communication system 300 may comprisean Evolved Serving Mobile Location Center (“E-SMLC”) 390 that isconnected to the core network 370 and a SUPL Positioning Center (“SPC”)395 (e.g., as described by the SUPL standards available from the OpenMobile Alliance (“OMA”)) that is connected with the location center 372.In some implementations, a location estimation component 350 may be asub-component of the E-SMLC 390.

The various access networks 340-344 are also connected to a core networkcomponent 370 that provides core network control, including switching orotherwise routing voice and/or data between location estimationcomponents 350; access networks 340-344; a Public Switched TelephoneNetwork (“PSTN”); a telephone switch such as a 5ESS switch, a PBXswitch; a data or IP network; a router; other switches; other corenetwork components; and/or the like. The core network component 370 mayinclude one or more discrete network components, including, inter alia,switches, a Mobility Management Entity (“MME”) (e.g., as described bythe System Architecture Evolution (“SAE”) standards available from the3GPP, such as by TS 33.40) and/or similar components that provide corenetwork control. Also, the core network component 370 may include aMobile Switching Center (“MSC”), a media gateway, a call gateway, and/orthe like. For simplicity, in FIG. 3, all the various discrete networkcontrol components are shown within a single, amalgamated core networkcomponent 370 since each discrete component provides similar oranalogous functionality. One having skill in the art will alsoappreciate that each discrete network component may be configured todirectly couple or interact with only a subset of the access networks340-344 and/or a subset of the discrete location estimation systemsrepresented by each location estimation component 350.

The core network component 370 is connected to a location center 372.The location center 372 is configured to send location estimationrequests to, and receive location data from, access networks 340-344,the location estimation component 350, E-SMLC 390 and/or SPC 395. To doso, the location center 372 is configured to request or determinerouting information (e.g., from a Home Subscriber Server). The locationcenter 372 may additionally perform administrative functions such asauthentication/security, privacy and billing. The location center 372may additionally be coupled to an Automatic Location IdentificationDatabase (“ALI database”) server and/or similar database servers thatmap phone numbers (or IP addresses or similar identifiers) to physicaladdresses or geographical locations. The location center 372 may includeone or more discrete location center components, including, inter alia,a Gateway Mobile Location Center (“GMLC”), a Location Retrieval Function(“LRF”) (e.g., as described by the IMS specifications and technicalreports of the 3GPP, Telecoms and Internet Converged Services andProtocols for Advanced Networks (“TISPAN”), or other standardsorganizations), a SUPL Location Center (“SLC”) (e.g., as described bythe SUPL standards available from OMA), and/or similar. For simplicity,in FIG. 3, all the various discrete location center components are shownwithin a single, amalgamated location center 372 since each discretecomponent provides similar or analogous functionality. Furthermore, forsimplicity, only a single connection is shown between the core networkcomponent 370 and the location center 372 However, one having skill inthe art will appreciate that each discrete location center component maybe configured to directly couple or interact with only a subset of theaccess networks 340-344, a subset of the discrete location estimationcomponents within the amalgamated location estimation component 350,and/or discrete core network components within the core networkcomponent 370.

The core network component 370 is also connected to an IP MultimediaSystem (IMS) 361, which interacts with other network components toprovide IP services to a mobile device. An IMS 361 may include a ProxyCall Session Control Function (“P-CSCF”), an Emergency Call SessionControl Function (“E-CSCF”), and Home Subscriber Server (“HSS”), e.g.,as described by the IMS specifications and technical reports of the3GPP, TISPAN or other standards organizations, including technicalreports TR 23.826, TR 23.870, and/or TR 23.167, all developed by the3GPP.

The IMS 361 is connected to a Session Continuity and Consistency Server(“SCC”) 384. Generally an SCC provides IMS-based mechanisms for enablingservice continuity of multimedia sessions. The SCC may implementfunctionalities such as handling access network transfers, mobile devicetransfers, and multiple media flows. SCC 384 may be an SCC as describedby the IMS specifications and technical reports of the 3GPP, TISPAN, orother standards organizations, including 3GPP Technical Specification23.237 V9.1.0. Although current implementations of an SCC enable variousaspects of session management within a single network, theseimplementations do not provide seamless location determinations acrossmultiple access networks and/or mobile devices as shown in FIG. 2.

Each of the discrete components within the location center 372 (e.g., aGMLC, LRF and/or SLC) is suitable for determining and serving thelocation of a mobile device as determined by a single access network.However, each of these discrete components takes a piecemeal approach tolocation determinations and thus typically these discrete componentscannot consistently provide position continuity and/or locationcontinuity across different access networks and different mobile devicesas shown in FIG. 2. In order to provide improved position continuityand/or location continuity as a user changes networks and/or devices, aLocation Continuity Application Server (LCAS) 376 is thereforeintroduced into the system. The LCAS 376 is coupled to location center372 via the SCC 384 and IMS 361 so it may initiate multiple locationestimations or determinations in multiple access networks and reconcilethe results of these multiple determinations.

As will be described in additional detail herein, LCAS 376 receiveslocation data, including positioning measurements or location estimates,from one or more components and subsystems within communications system300 or from other communications systems. The LCAS 376 stores thereceived data in a location database (“DB”) 386, and uses the receiveddata in order to accurately determine a location of a mobile deviceusing various location determination methods. The determined location isprovided to emergency, commercial, and/or other location-based services.In one example, LCAS 376 is configured to provide determined locationinformation to a PSAP, e.g., as part of an E911 service. LCAS 376 mayalso be configured to provide determined location information to anyother entity or for any other purpose. For example, LCAS may beconfigured to provide determined location information to mobile deviceusers, network operators or network components, third-partylocation-based service providers, remote telemetry users, advertisers,and/or the like.

Although shown as a discrete component, some or all of the functionalityof the LCAS 376 may be performed by the SCC 384. Additionally oralternatively, some or all of the functionality of the LCAS may beperformed in whole or in part by a mobile device 110, 112, 114 (e.g., bya location continuity stack application resident therein) and/or one ormore other system components, including the location estimationcomponent 350. To simplify system architecture, the LCAS may providesome of the functionality that is typically provided by a service brokerwithin the IMS 361 and/or may interact with a service broker within theIMS. The LCAS 376 is described in greater detail with respect to FIG. 4.

While communications system 300 is illustrated and described in terms of2G, 3G, 4G, IP RAN, and hard-wired network components and architecture,the system is not limited to such technologies. Any suitablecommunications system may employ aspects of the invention describedherein. Additionally, while FIGS. 1-3 illustrate specific examples ofsuitable environments and communications systems in which aspects of theinvention may be practiced, various modifications, such as the inclusionof additional components, consolidation and/or deletion of variouscomponents, and shifting of functionality from one component to anothermay be made without deviating from the invention.

Location Continuity Application Server (“LCAS”)

FIG. 4 is a block diagram of the LCAS 376. As shown, LCAS 376 comprisesa selection module 402, a request module 404, an analysis module 408,and a database management module 410.

The LCAS 376 facilitates continuous positioning measurements andlocation determinations in response to a request to locate a mobiledevice 110, 112, 114. The request that the LCAS locate a mobile devicemay be received at any time, regardless of whether the mobile device ispowered on, powered off, in use, or sitting idle. For example, a requestmay be received prior to, during, and/or after a call is made on themobile device. A request from a service for the location of a mobiledevice may be received only once (e.g., to provide a map for the mobiledevice), or may be received frequently (e.g., during an emergency eventwhere it may be important to accurately track the movement of the mobiledevice at all times).

The selection module 402 receives the request for the location of themobile device from a requesting service and selects a suitable locationdetermination method or methods for the system to utilize in order tolocate a particular mobile device in a manner that is responsive to therequesting service. The selection module 402 may analyze any relevantcriteria to select a suitable location determination method or methods.Criteria used in the selection process include:

-   -   The type, make, model, or capabilities of the mobile device 110,        112, 114 being located.    -   The types of access networks currently or previously available        to the mobile device being located and related criteria, such as        a network's signal strength at the mobile device.    -   The quantity, quality and nature of stored historical location        data for the mobile device, including historical positioning        measurements, estimated locations, and reference locations.    -   The quality of service (“QoS”) required by the requesting        location-based service. For example, the QoS metrics required        for an emergency service may be more stringent than for a        navigation application or a location-based search application.        The QoS may include both location accuracy and timeliness of        location response.    -   The costs or resources associated with using the various        determination methods.    -   Any other current or past session factors, such as the IMS used        (e.g., a home IMS or visited IMS), core IP network used (e.g., a        home core IP network versus a visited core IP network),        application used, application session, and applicable charging        scheme.

More details regarding the selection of one or more suitable locationdetermination methods may be found in assignee's U.S. patentapplication, Ser. No. 12/467,201, filed May 15, 2009, entitled “Facilityfor Selecting a Mobile Device Location Determination Technique”(Attorney Docket No. 314198092US), which is incorporated herein in itsentirety.

When selecting a suitable location determination method, selectionmodule 402 is not limited to selecting only a single locationdetermination technique implemented by a single access network. Instead,selection module 402 may identify two or more determination techniquesthat are implemented by different access networks and specify a processto analyze the results of those two or more techniques. To indicate theappropriate method of utilizing various location determinationtechniques, the selection module specifies a reconciliation process thatis suitable for the location request. The reconciliation process isimplemented by the request module 404 and analysis module 408. Areconciliation process is generally a data structure or otherinformation source that contains a set of rules, methods, preferences,priorities, and parameters for utilizing two or more kinds of locationdetermination techniques that are implemented by two or more accessnetworks. The reconciliation process may be generated from scratch basedon certain criteria such as the specific conditions detected by theselection module, or may be selected from a set of stored reconciliationprocesses that are maintained by the selection module 402.

A reconciliation process may dictate that two or more parallel locationestimation processes be initiated to guard against failures orinaccuracy of any one location estimation process. The selection module402 might require this type of reconciliation process if thelocation-based service requesting location data requires a high qualityof service regardless of cost. The selection module 402 might alsorequire this type of reconciliation process for an emergency (e.g.,E911) service. As an example, the LCAS initiates a primary method oflocation determination (e.g., AGPS or U-TDOA), and one or more backupmethods of location determination (e.g., CI-RTT, hybrid RTT, and/orLTE-based methods). If the primary method of location determinationfails to produce location estimates with a desired accuracy oruncertainty (or satisfy other performance metrics, such as a desiredtime to fix (“TTF”)), the LCAS may instead utilize results from one ormore backup methods.

To describe a parallel location estimation, a reconciliation processindicates which location determination methods should be initiated inwhich access networks and when and how these methods should beinitiated. For example, a reconciliation process may configure thesignaling period for a particular access network and/or mobile device110, 112, 114. The reconciliation process provides rules and parametersfor selecting between the results of a primary and backup locationestimation method. For example, a reconciliation process may indicatethe accuracy, TTF, and/or other performance metrics that must beachieved by a primary or backup method. As another example, areconciliation process may provide a rank ordering of backup methods.

A reconciliation process may also provide various rules, methods, andparameters for utilizing positioning measurements, location estimates,and/or other location data that is provided by a visited communicationssystems 300. Such a reconciliation process may permit the system toprovide greater positioning and location continuity when a mobile deviceroams outside its home communications system 300.

A reconciliation process may also indicate how to utilize positioningmeasurements, estimated locations and/or other location data that weregenerated for different mobile devices. For example, a reconciliationprocess may indicate how positioning measurements and/or estimatedlocation data generated for one or more mobile devices 110, 112, 114 maybe used to determine the location of another mobile device. For example,a reconciliation process may specify that if one mobile device 110 ownedby a particular user cannot be located with sufficient accuracy (or witha certain TTF), that the system should utilize the determined locationof another mobile device 112 owned by or otherwise associated with thesame user.

As another example, a reconciliation process may indicate howpositioning measurements and/or estimated locations generated for onesession may be used to determine the location of a mobile device duringanother session. For example, a reconciliation process may specify thata location estimate generated previously by a GSM network for anavigation program on a mobile device may be provided to alocation-based search running on the same mobile device. This priorlocation estimate may be provided to the location-based searchapplication until an overlapping UMTS network generates a new locationestimate having sufficient accuracy.

These examples of reconciliation processes are intended to beillustrative, not exhaustive. The selection module 402 may indicate areconciliation process that blends elements of these examples orutilizes other suitable location determination approaches. Variousexamples of reconciliation processes are described in greater detailherein.

The request module 404 initiates location estimations in various accessnetworks and/or retrieves location data such as estimated locations andpositioning measurements from various access networks in accordance witha reconciliation process. To do so, the request module 404 may requestthat the location center 372, a mobile device 110, 112, 114, and/oranother system component initiate positioning measurements and/orlocation determinations in one or more access networks and/or providelocation data for a mobile device. In some implementations, the requestmodule 404 may utilize the IMS 361 to relay such a request.

The analysis module 408 analyzes various location data that are receivedor accessed from various access networks as a result of the requestsmade by the request module 404, including positioning measurement dataand/or estimated location data. The analysis module 408 applies thespecified reconciliation process to the various data sets to generate aset of determined locations that LCAS 376 may utilize. Databasemanagement module 410 is responsible for maintaining, updating, andproviding access to positioning measurements, estimated locations, andother location data stored in location database 386. For example, thedatabase management module maintains positioning measurement data and/orestimated location data generated by various access networks that wererequested by request module 404 or received by analysis module 408.Database management module also maintains determined location datagenerated by analysis module 408 based on the applied reconciliationprocess. In response to a request for location data, the databasemanagement module 410 provides the requested positioning measurementdata and/or estimated location data.

The LCAS 376 provides the determined location of the mobile device tothe requesting service. The requesting service may be a PSAP or anotheremergency location-based service, another system component (e.g., anE-CSCF, P-CSCF or a system component that performs network registrationor billing functions) within the same or a different communicationssystem an LCAS associated with a different communications system, or anyother requesting service (e.g., a navigation application, an assettracking or recovery service, another non-emergency location-basedservice, etc.). The requesting service may be operated by commercialentities and/or non-commercial entities (e.g., governmental, nonprofit,or other non-commercial entities). The location information may beprovided for free, or a charge may be levied against the requestingservice and/or a user of a mobile device 110, 112, 114 when the locationdata is provided.

Alternatively or additionally, the memories of mobile devices 110, 112,114 may store a location continuity stack application in order toimprove location continuity and/or position continuity over a callsession and/or other type of session. In some implementations, alocation continuity stack application may perform some or all of thefunctionality of LCAS 376, including the functionality provided by itsselection module 402, request module 404, and/or analysis module 408.For example, a location continuity stack application may be configuredto permit a mobile device to simultaneously register with two or moreaccess networks, and/or to continuously conduct positioning measurementsand/or location estimations with two or more access networks. As anotherexample, a location continuity stack application may be configured topermit a mobile device to seamlessly initiate positioning measurementsand/or location estimations with a newly accessed network. As yetanother example, a location continuity stack application may beconfigured to permit a mobile device to analyze multiple sets oflocation data (e.g., estimated locations) provided by various accessnetworks.

Those skilled in the art will appreciate that the LCAS 376 may beimplemented on any computing system or device. Suitable computingsystems or devices include personal computers, server computers,multiprocessor systems, microprocessor-based systems, network devices,minicomputers, mainframe computers, distributed computing environmentsthat include any of the foregoing, and the like. Such computing systemsor devices may include one or more processors that execute software toperform the functions described herein. Processors include programmablegeneral-purpose or special-purpose microprocessors, programmablecontrollers, application specific integrated circuits (ASICs),programmable logic devices (PLDs), or the like, or a combination of suchdevices. Software may be stored in memory, such as random access memory(RAM), read-only memory (ROM), flash memory, or the like, or acombination of such components. Software may also be stored in one ormore storage devices, such as magnetic- or optical-based disks, flashmemory devices, or any other type of non-volatile storage medium forstoring data. Software may include one or more program modules whichinclude routines, programs, objects, components, data structures, and soon that perform particular tasks or implement particular abstract datatypes. The functionality of the program modules may be combined ordistributed across multiple computing systems or devices as desired invarious embodiments.

Location Data Storage

FIG. 5 shows a table 500 that conceptually illustrates the type oflocation data or information generated and stored by LCAS 376 and itscomponents in location database 386. As used herein, the terms “locationdata” or “location information” include positioning measurements (e.g.,range measurements of a mobile device within a network) and estimatedlocations (e.g., an estimate of the latitude, longitude and/or altitudeof a mobile device and, in some implementations, the time and/orestimated or calculated uncertainty or accuracy of the locationestimate). As described herein, the location data in location database386 may be utilized in location determination techniques or to otherwiseimprove position and/or location continuity. As an example, storedlocation data for one mobile device may be utilized to locate a secondmobile device. As another example, to improve location continuity,location data in location database 386 may be sent to a visitedcommunications system when a mobile device roams into the visitednetwork.

The location data in location database 386 may also be utilized forvarious commercial and non-commercial purposes, such as marketingintelligence, network registration, billing/charging, location-basedadvertising campaigns, remote telemetry, social networking technologies,or any other location-based service that may benefit from mininghistorical location data. Additional examples include asset tracking orrecovery services, customer analytics, and mobile device security.

As shown in FIG. 5, the table 500 includes columns for a sessionidentifier (“ID”) 505 and a mobile device ID 510. A session ID is aglobally or locally unique identifier for a particular session and adevice ID is a globally or locally unique hardware identifier for amobile device 110, 112, 114. Each row 545, 550, 555, 560 in table 500corresponds to a unique combination of a session and device. Forexample, the first and second rows 545, 550 each correspond to sessionID “A3F1,” but the two rows have different device IDs (“LL13” and“DJ82,” respectively).

Table 500 may have additional columns (not shown) that reflect othersession or state factors related to a row. For example, table 500 mayhave additional columns that reflect the application(s), accessnetwork(s), and/or core IP network(s) used during a session. Each entryin these additional columns may reflect either a single static value, ormay reflect a time series (for example, to reflect how a mobile devicemoved from one access network to another over time). In someimplementations, each row may correspond to a different combination ofsession factors (and/or other factors). For example, table 500 may havea separate row for each unique combination of a session, device, andapplication (e.g., a navigation application versus a location-basedsearch application).

Columns 525-540 in table 500 reflect estimated locations for eachsession/device pair generated by a particular type of access networkusing a particular type of location determination technique. Forexample, column 525 may include estimated locations generated by a firstaccess network (e.g., a GSM network) using a first locationdetermination method (e.g., U-TDOA) while column 530 may includeestimated locations generated by the first access network (e.g., thesame GSM network) using a second location determination method (e.g.,AGPS). As another example, column 535 may include estimated locationsgenerated by a second access network (e.g., a UMTS network) using thesecond location determination method (e.g., AGPS). As shown, there maybe any number of additional columns 565, each of which corresponds to aunique combination of an access network and a location determinationmethod.

As indicated in FIG. 5 with the text [t],” each individual entry incolumns 515-540 may reflect a time series of estimated locations. Eachentry in these columns may have one, none, or multiple locationestimates, where each location estimate is associated with a particularpoint in time. Furthermore, each location estimate may be expressed as arange or confidence window indicating a two- or three-dimensionalgeographical area (e.g., +/−5 meters) or may be associated with anestimated or calculated accuracy or uncertainty. As shown, not everycombination of access network and device will contain estimatedlocations. A particular device may not utilize a particular accessnetwork or a particular location determination technique may not havebeen used to estimate the location of a device. For example, as shown bythe text “NULL” at row 555, column 540, the device “A6N5” has notutilized Network 3. As another example, as shown at row 550, column 530,the device “D82” utilized Network 1, but as shown by the text “NULL” atrow 550, column 525, Network 1 did not estimate its location usingMethod 1.

Additionally or alternatively, although not shown, table 500 may includecolumns that represent raw positioning measurement data (e.g., rangemeasurements of a mobile device within a network, a cell identity, abase station latitude or longitude, etc.) or additional informationrelated to the derivation of estimated locations generated by variousaccess networks. For example, table 500 may include a column forreference locations that were generated by various access networks. Asan example, the “L3[t]” entry at row 545, column 535 may represent theestimated location of a mobile device “LL13” at various time points asdetermined by Access Network 2 using an AGPS technique. In this example,table 500 may include an additional column (not shown) that stores theAGPS reference location(s) used to calculate L3[t]. As another example,an entry in table 500 may be associated with one or more identifiers ofa cell, femtocell, picocell, access point, base station, Node-B,eNode-B, cell site, and/or other network component or network that wereaccessible to the mobile device, and that were utilized to estimate thelocation of the mobile device associated with that row. For example,table 500 may associate an entry with a time series of identifiers thatreflects how a mobile device moved from one base station (BTS 340) toanother within a particular access network.

Table 500 also includes columns for estimated locations that aregenerated using a reconciliation process that is applied by the LCAS.For example, column 515 contains a location that was determined by areconciliation process H1, and column 520 contains a location that wasdetermined by a reconciliation process H2. The table may have any numberof additional columns each reflecting locations that are generated by adifferent reconciliation process. Entries in these columns may have beengenerated using the other various entries in the table (i.e., theestimated location, positioning measurement data, or related informationthat is generated by various access networks). As indicated by the text“F1[[L1[t]−Ln[t]],” for example, a determination method that is used togenerate data in column 515 may functionally combine or otherwiseutilize location data that is generated for other mobile devices, othersession factors, or other sessions altogether.

Initiating and Utilizing Multiple Parallel Location Estimations

FIG. 6 is a logical flow diagram of a process 600 for initiating andutilizing multiple parallel location estimations by one or more accessnetworks. LCAS 376, its components, or another suitable system mayperform process 600 in order to provide determined locations in responseto a request from an emergency or non-emergency location-based serviceto locate a mobile device. By using parallel location estimations fromvarious access networks in process 600, the location continuity servicemay improve accuracy, yield, and/or TTF when locating a mobile device.As an example, process 600 may initiate three parallel locationestimations in two access networks, such as one primary determinationand two backup estimations, to prevent delays and/or inaccuracies thatmight otherwise result if a positioning measurement and/or locationestimation using the primary method fails.

Process 600 begins at block 605, when LCAS 376 utilizes selection module402 to generate or select a reconciliation process that is applicable tothe mobile device 110 based on the available access networks and/orother applicable criteria, as described previously. The selection modulespecifies a reconciliation process that gracefully handles failedpositioning measurements and/or failed location estimations. Thereconciliation process that is generated indicates which locationestimation or determination method to initiate in which access networks,and when and how to initiate these methods. The generated reconciliationprocess also provides rules and parameters for selecting between theresulting estimated locations determined by the selected locationestimation methods.

For example, selection module 402 may specify a reconciliation processfor a mobile device that requires an available GSM network to perform aU-TDOA location estimation for the mobile device 110, and an overlappingUMTS network to also simultaneously perform AGPS and OTDOA locationestimations for the mobile device. The specified reconciliation processmay dictate that AGPS location estimates should be utilized to locatethe device except for time points where AGPS produces estimates havingaccuracy worse than 100 meters. In this example, the reconciliationprocess may further dictate that in the event that the AGPS method failsto produce results of the desired accuracy or uncertainty, the moreaccurate (or less uncertain) of the two backup methods (OTDOA andU-TDOA) should be utilized to determine the location of the device.

At block 610, LCAS 376 initiates one or more location estimations ordeterminations in one or more access networks in accordance with thereconciliation process. For example, in accordance with the previousexample of a reconciliation process, the LCAS may request a GSM networkto perform a U-TDOA location estimation for a mobile device 110, and anoverlapping UMTS network to also simultaneously perform AGPS and OTDOAlocation estimations for the same mobile device.

At block 620, LCAS 376 waits for location data (e.g., locationestimates) during a temporal window. The length of the temporal windowmay vary depending on the types of location estimations that wererequested and/or other factors such as the accuracy or TTF required bythe location-based service that will utilize the results of process 600.For example, in some implementations, the length of the temporal windowmay be chosen so that even the location determination method having thelongest TTF and/or other latencies may return an estimated location. Inother implementations, the temporal window may be chosen so that thefunctions described in blocks 620-660 may be performed within the TTFrequired by the location-based service that will utilize the results ofprocess 600. The applicable reconciliation process may include aparameter that dictates the length of the temporal window used.

At block 620, LCAS 376 also receives one or more sets of location data(e.g., location estimates) from one or more access networks during thetemporal window. For example, LCAS may receive from a GSM access networkone set of location estimates generated by a U-TDOA method, and from aUMTS access network two sets of location estimates that are generated byAGPS and OTDOA techniques. Each data set may include one or moreestimates of the location of a mobile device 110 at a certain timepoint. The various location data sets may include location estimates fordifferent time points. In addition to estimated locations, LCAS mayreceive other location data or other information from the one or moreaccess networks. LCAS may receive an indication that one or morelocation determination methods failed to either take a positioningmeasurement and/or fix the location of the mobile device with sufficientaccuracy. For example, LCAS may receive an indication from a UMTSnetwork that an AGPS estimation method failed entirely due to lack ofsatellite visibility. LCAS may also receive an indication of theestimated accuracy or uncertainty of a location estimate. For example,an LCAS may receive an indication that a location estimated using aU-TDOA method is within 65 meters of the actual location of the mobiledevice being located. LCAS may also receive positioning measurement data(e.g., range measurements) and/or state or session information.

Instead of an LCAS 376 initiating a location determination by an accessnetwork, an access network may automatically push positioningmeasurements and/or estimated locations to the LCAS without interventionby the LCAS. For example, an access network may automatically provide anestimated location on a periodic basis. Alternatively, at blocks 620 and630, rather than waiting for and receiving location data, an LCAS mayactively pull positioning measurements or estimated locations from oneor more access networks.

At block 640, LCAS 376 determines the location of a mobile device 110 atone or more time points during the temporal window using the one or morereceived sets of location data, stored location data, including receivedor stored location estimates and positioning measurements. To make thisdetermination, the LCAS applies the rules, methods, preferences,priorities, and parameters for utilizing one or more kinds of locationestimation techniques that are specified in the applicablereconciliation process. For example, in accordance with the examplereconciliation process described above, LCAS may utilize an estimatedlocation that is generated by a preferred or primary locationdetermination method (e.g., AGPS), so long as the preferred method didnot fail and/or the estimated location produced by the preferred methodhas an accuracy that exceeds a threshold value (e.g., is accurate towithin 100 meters or less). As another example, in accordance with adifferent type of reconciliation process, LCAS 376 may determine thelocation of the mobile device 110 to be the location estimate that mostaccurately reflects the mobile device's actual location. To determinethe most accurate location estimate, the LCAS may either utilizeaccuracy or uncertainty information received from the various accessnetworks or access a table or data store that correlates variouslocation determination methods to average accuracy or uncertainty.

At block 650, LCAS 376 stores and/or serves the determined location atone or more time points to the requesting service, such as a commercialservice and/or emergency service. LCAS may also invoke databasemanagement module 410 to store the determined location. For example,database management module 410 may store one or more determinedlocations in column 515.

At block 660, LCAS 376 stores some or all of the location data receivedfrom the various access networks in location database 386 and may alsostore the additional information received from the one or more accessnetworks therein. To illustrate, LCAS may add received U-TDOA data tocolumn 540, OTDOA data to column 525, and AGPS data to column 530.

At decision block 670, LCAS 376 determines if there is an additionaltemporal window to process. For example, LCAS may determine if anemergency call with a mobile device 110 is still active, and thus thelocation of the mobile device is still needed. As another example, theLCAS may determine if a non-emergency location-based service (e.g., anavigation program) needs additional location data for a new temporalwindow. If there is another temporal window in which the location of themobile device should be determined, LCAS proceeds to block 675.Otherwise the process 600 returns.

At decision block 675, the LCAS 376 determines if the set of accessnetworks available to the mobile device 110 has changed. For example,the LCAS may determine that the mobile device has moved out of range ofa UMTS access network. Although not shown, the LCAS may also determineif other relevant session factors or process criteria have changed(e.g., the application used to make a call). If the access networks orother key session factors have changed, the process 600 repeats startingat block 605, where the LCAS specifies a new reconciliation process.Otherwise, the process repeats starting at block 620.

Roaming Use Cases

During a period of its operation, a mobile device 110 may move from ahome access network within a home communications system (such ascommunications system 300) to a visited access network in a visitedcommunications system, or vice versa. To seamlessly maintainlocation-based services involving a mobile device during its handofffrom a first communications system to a second communications system, anLCAS from the first communications system (a “first LCAS,” such as LCAS376) and an LCAS from the second communications system (a “second LCAS”)may coordinate in order to maintain position continuity and locationcontinuity across the handoff.

To improve the performance of its location determinations and/or toimprove position continuity and/or location continuity following acommunications system handoff, a second LCAS may request from a firstLCAS historical location data (e.g., location estimates and/orpositioning measurement data) generated by the first LCAS and/or accessnetworks within the first communications system. The second LCAS mayprovide historical location data generated by the first LCAS to alocation-based service until the second LCAS is able to perform its owndetermination of the location of a mobile device. Alternatively oradditionally, a second LCAS may extrapolate historical location datagenerated by a first LCAS to generate an estimated location. The secondLCAS provides this estimated location to a location-based service untilthe second LCAS is able to perform its own determination of the locationof a mobile device 110 using the positioning measurements and locationestimates of one or more access networks located in the secondcommunications system. In this way, a location-based service may receivesome indication of the location of the mobile device from the secondcommunications system immediately after a handoff.

FIGS. 7A, 7B, and 8 illustrate three processes for improving positioncontinuity and location continuity across a handoff from onecommunications system to another.

FIG. 7A is a logical flow diagram of a process for providing improvedlocation continuity when a mobile device roams from a home accessnetwork to a visited access network. Although not shown, when process700 begins, a mobile device is registered with one or more home accessnetworks within a home communications system.

When the mobile device is utilizing a home access network, alocation-based service requests an LCAS within a home communicationssystem (a “home LCAS,” such as LCAS 376) to generate and providedetermined location data for the mobile device to the location-basedservice. For example, the user may initiate a navigation application onhis mobile device that may request determined location data from thehome LCAS.

In response to this request, the home LCAS may initiate a process likethe one shown in FIG. 6, or another suitable process, to determine thelocation of the mobile device within the home access network. Forexample, the home LCAS may initiate one or more location estimations inone or more home access networks, receive one or more sets of locationdata from one or more home access networks, and analyze the data sets togenerate a set of determined locations that it provides to thelocation-based service. Thus, as shown at block 710, a home LCASgenerates a first set of determined location data from one or more setsof location data that were generated by home access networks.Additionally, at block 710, the home LCAS may receive and/or analyzeother information generated by one or more home access networks.

Between blocks 710 and 715, the mobile device registers with and beginsutilizing a visited access network instead of a home access network.That is, the mobile device registers with an access network that is partof a visited communications system. As shown at block 715, the home LCASreceives a notification that the mobile device has moved or roamed to avisited access network. For example, the notification may come from acomponent of the visited communications system, such as an LCAS in thevisited communications system (the “visited LCAS”). The home LCAS maynotify the location-based service of the change in communications systemso that the location-based service may request determined location datafrom the visited LCAS. Alternatively or additionally, the home LCAS maynotify the visited LCAS of the ongoing request by the location-basedservice to receive location information about the mobile device. In thisway, the home LCAS redirects or otherwise connects the location-basedservice to a visited LCAS within the visited communications system.Alternatively or additionally, the location-based service may detect thechange in the network and automatically request determined location datafrom a visited LCAS on an ongoing basis.

As described previously, to improve position and location continuity,the visited LCAS may utilize historical location data generated by thehome LCAS and/or home access networks. Thus, as shown at decision block72 0, the home LCAS determines if it has received a request from thevisited LCAS for historical location data generated by the home LCASand/or home access networks. If the home LCAS does receive such arequest, as shown at block 725, it may send to a visited LCAS the firstset of determined location data that was generated at block 710. Thehome LCAS may also send some or all of the location data it receivedfrom home access networks prior to block 710. The process 700 thenreturns. Otherwise, if no request is received, the process 700 returns.

FIG. 7B is a logical flow diagram of a process 750 for determining thelocation of a mobile device after the device roams from a home accessnetwork to a visited access network. Such a determination may be usefulfor one or more purposes. For example, if redirecting a requestinglocation-based service from a home LCAS to a visited LCAS will take asubstantial amount of time, the home LCAS may continue to providelocation estimates to the location-based service in the interim periodimmediately following the handoff. As another example, the home LCAS maystore determined location data generated by a visited LCAS in thelocation database 386 so that the home LCAS can provide a richer set ofhistorical location data to other location-based services that minehistorical location data such as billing services, asset tracking,customer analytics, and mobile device security services.

The process 750 begins at block 755, when the home LCAS generates afirst set of determined location data using location data (e.g.,location estimates) generated by home access networks. At block 760, thehome LCAS receives a notification that the mobile device has moved orroamed to a visited access network (i.e., the mobile device has startedroaming in a visited access network). At block 760, the home LCAS mayalso receive a notification indicating the type of visited accessnetwork and/or the location determination capabilities of the visitedaccess network. For example, the home LCAS may receive an indicationfrom a visited LCAS that the mobile device has roamed into a UMTSnetwork capable of performing only AGPS and OTDOA location estimations.It will be appreciated that blocks 750 and 760 are the same as blocks710 and 715 in FIG. 7A, and may reflect the same LCAS process. As shownat block 762, the home LCAS utilizes the received indication of accessnetwork and/or location determination capabilities to specify or updatethe reconciliation process that is applicable to the roaming mobiledevice. When updating the reconciliation process, the LCAS may use theinformation about the visited access network as selection criteria.

At block 765, the home LCAS queries the visited LCAS for the determinedor estimated location of the roaming mobile device, and/or otherlocation data, such as positioning measurement data that was generatedby the visited LCAS and/or visited access networks. At block 770, thehome LCAS receives a second set of location data and/or otherinformation requested from the visited communications system. Forexample, the visited LCAS may send a set of determined location data tothe home LCAS. Alternatively, the visited LCAS may automatically pushsuch location data to the home LCAS without a query from the home LCAS.

At block 780, the home LCAS utilizes the first and second sets oflocation data generated by the home access networks, visited LCAS and/orvisited access networks to determine the location of the mobile devicefor one or more time points. To make this determination, the LCASapplies the rules, methods, preferences, priorities, and parametersreflected in the reconciliation process that are applicable to theroaming mobile device.

At block 785, the home LCAS may serve determined location data (and/orreceived location data) to a location-based service. As one example, thehome LCAS may serve determined location data to the first location-basedservice that initiated tracking of the mobile device. Serving locationdata to the first location-based service may not be necessary if thefirst location-based service receives sufficient location informationfrom the visited LCAS. Serving location data to the first location-basedservice may be necessary, however, if the first location-based serviceexperiences delays when connecting to the visited LCAS after thehandoff, is unable to be handed-off to the visited system, or otherwiseis permanently or temporarily unable to receive location data from thevisited LCAS. Additionally or alternatively, the home LCAS may servelocation data to a second location-based service that is different fromthe first service. For example, even if a mobile device was originallylocated for the purposes of providing location data to a navigationprogram, at block 785, the home LCAS may serve determined location datato an asset tracking service or a location-based advertising service. Inthis way, the home service provider may derive additional value from thelocation determinations performed by both the home and visitedcommunications systems.

Also at block 785, the home LCAS may store the location data (e.g.,location estimates, positioning measurement data, and/or otherinformation) received from home access networks and/or the visitedsystem. Although not shown, blocks 765-785 may be repeated one or moretimes to determine the location of the mobile device during additionaltime windows. The process 750 then returns.

FIG. 8 is a logical flow diagram of a process 800 for determining thelocation of a mobile device when the device was roaming in a visitedaccess network and then returns to a home access network. Before process800 begins, a mobile device is registered with one or more visitedaccess networks in a visited communications system. When the device isregistered with the visited access network, a location-based servicerequests that a visited LCAS determine and provide the location of themobile device to the location-based service. For example, while roaming,a user may initiate a navigation application on his mobile device thatrequests location data from a visited LCAS. In response to this request,the visited LCAS determines the location of the roaming mobile device,serves the determined location information to the location-basedservice, and/or stores the location data. After the visited LCAS hasgenerated determined location data, the roaming mobile device registerswith a home access network instead of the visited access network.

The process 800 begins at block 810, when the home LCAS receives anotification that the previously-roaming mobile device has returned toits home communications system (e.g., from the mobile device or acomponent of the home communications system, such as the IMS). The homeLCAS may relay this notification to a visited LCAS within the visitedcommunications system. The visited LCAS may in turn notify thelocation-based service of the handoff so that the service may requestdetermined location data from a component of the home communicationssystem (e.g., home LCAS). Alternatively or additionally, the visitedLCAS may notify the home LCAS of the ongoing request by thelocation-based service to receive location data about the mobile device.In this way, the visited LCAS gracefully connects the location-basedservice to the home LCAS to ensure better location continuity.Alternatively or additionally, the location-based service may detect thechange in network and automatically request updated determined locationdata from the home LCAS on an ongoing basis. In any of these scenarios,as shown at block 820, the home LCAS receives a request from thelocation-based service to provide determined location data to theservice shortly after the mobile device returns to a home accessnetwork.

At block 810, the home LCAS may also receive a notification indicatingthe type of visited access network into which the mobile device roamed,the location determination capabilities of the visited access network,and an indication of the availability of historical location data (e.g.,estimated locations and/or positioning measurement data) generated bythe visited LCAS and/or visited access networks. For example, the homeLCAS may receive an indication from a visited LCAS that the mobiledevice had roamed into a UMTS network capable of performing only AGPSand OTDOA location estimations, and that recent AGPS and OTDOA locationestimates are available.

At block 830, to begin fulfilling the request by the location-basedservice, the home LCAS specifies a reconciliation process for the mobiledevice. When generating the reconciliation process, the selection module402 may use the received information about the visited access networkand the availability of historical location data as selection criteria.For example, the selection module may create a reconciliation processthat dictates that the home LCAS should obtain the most recenthistorical AGPS location estimate generated by the visitedcommunications system and utilize this historical location estimateuntil an AGPS location determination in a home access network has fixedthe position of the mobile device with sufficient accuracy. By utilizinghistorical data from a visited communications system, the home LCAS mayimprove the TTF, accuracy, cost, and/or yield of its own locationdeterminations and improve location continuity.

At block 840, in accordance with the specified reconciliation process,the home LCAS requests, from the visited LCAS, historical location data(e.g., estimated locations and/or positioning measurement data)generated by the visited LCAS and/or visited access networks. Forexample, the home LCAS may request that the visited LCAS providehistorical AGPS estimated locations for the most recent time pointsavailable. The request may be general in nature (e.g., a request for thelast available location determination for the roaming mobile device) ormore specific (e.g., a request for any AGPS location estimates availablefor the last minute that the mobile device was roaming in the visitednetwork). The nature of the request may be dictated by thereconciliation process and the capabilities of a visited LCAS to providerich historical data.

At block 850, the home LCAS receives from the visited LCAS a first setof historical location data (e.g., location estimates and/or positioningmeasurement data) generated by the visited LCAS and/or visited accessnetworks. Although not shown, the home LCAS may also initiate one ormore location estimations in one or more home access networks inaccordance with the applicable reconciliation process.

At block 860, the home LCAS receives a second set of location data fromone or more home access networks. For example, the home LCAS may receiveestimated locations that are generated by a home access network using anAGPS determination method. Although not shown, to improve locationcontinuity, between blocks 850 and 860, the home LCAS may servehistorical location data received from the visited LCAS to therequesting location-based service.

At block 870, the home LCAS determines the location of the mobile deviceusing the first and second sets of location data. To make thisdetermination, the home LCAS applies the rules, methods, preferences,priorities, and parameters reflected in the reconciliation process.

At block 880, the home LCAS may serve the determined location to alocation-based service. As one example, the home LCAS may servedetermined location data to the first location-based service thatinitiated the tracking of the mobile device. Additionally oralternatively, the home LCAS may serve location data to a secondlocation-based service that is different from the first service. Forexample, even if a mobile device was originally located for the purposesof providing location data to a navigation program, the home LCAS mayserve determined location data to an asset tracking service or alocation-based advertising service. Also at block 880, the home LCAS maystore the determined location and/or the sets of location data and otherinformation received from home access networks and/or the visitedsystem. Although not shown, as necessary, blocks 860-880 may be repeatedone or several times to generate additional determined locations atadditional time points. The process 800 then returns.

FIGS. 7A, 7B, and 8 describe how a first LCAS associated with a firstcommunications system and a second LCAS associated with a secondcommunications system exchange location data. However, one having skillin the art will appreciate that in other examples, a first LCAS maydirectly request location data from and/or exchange location data withother components of a second communications system. For example, a firstLCAS may directly request and/or receive information from an accessnetwork associated with a second communications system. Moreover, theprocesses described herein may be utilized across multiplecommunications systems, such as when a mobile device roams from a firstcommunications system to a second, third, and fourth communicationsystem.

CONCLUSION

The above Detailed Description of embodiments of the system is notintended to be exhaustive or to limit the system to the precise formdisclosed above. While specific embodiments of, and examples for, thesystem are described above for illustrative purposes, various equivalentmodifications are possible within the scope of the system, as thoseskilled in the relevant art will recognize. For example, while processesor steps are presented in a given order, alternative embodiments mayperform routines having steps, or employ systems having steps, in adifferent order, and some processes or steps may be deleted, moved,added, subdivided, combined, and/or modified to provide alternative orsubcombinations. Each of these processes or steps may be implemented ina variety of different ways. Also, while processes or steps are at timesshown as being performed in series, these processes or steps may insteadbe performed in parallel, or may be performed at different times.

While certain aspects of the invention are presented below in certainclaim forms, the applicant contemplates the various aspects of theinvention in any number of claim forms. Accordingly, the applicantreserves the right to add additional claims after filing the applicationto pursue such additional claim forms for other aspects of theinvention.

1. A method for determining an estimated location of a mobile devicethat is in range of two or more overlapping access networks, the methodcomprising: specifying a reconciliation process applicable to a mobiledevice that is in range of two or more overlapping access networks,wherein the mobile device is capable of registering with the two or moreoverlapping access networks and obtaining location data from the two ormore overlapping access networks; initiating, in accordance with thespecified reconciliation process, location estimations of the mobiledevice in at least two of the overlapping access networks; receiving,during a time window, one or more sets of location data for the mobiledevice generated by the initiated location estimations in the two ormore overlapping access networks; and determining, in accordance withthe specified reconciliation process, an estimated location of themobile device using the one or more received sets of location data. 2.The method of claim 1, wherein the reconciliation process indicates howthe location estimation methods should be initiated in the two or moreoverlapping access networks.
 3. The method of claim 1, wherein thereconciliation process provides rules for selecting between receivedsets of location data if two or more sets of location data are receivedfrom the indicated location estimation methods.
 4. The method of claim3, wherein the rules for selecting between received sets of locationdata specify an accuracy to be achieved by an indicated locationestimation method.
 5. The method of claim 4, wherein the rules forselecting between the received sets of location data further specifyselecting the most accurate set of location data.
 6. The method of claim3, wherein the rules for selecting between received sets of locationdata specify a time to fix to be achieved by an indicated locationestimation method.
 7. The method of claim 3, wherein the rules forselecting between received sets of location data specify a rank orderingof the two or more location estimation methods.
 8. The method of claim1, wherein specifying the reconciliation process comprises analyzing oneor more criteria selected from the group consisting of: characteristicsof the mobile device; an identity of access networks from which themobile device is currently capable of receiving location data; anidentity of access networks from which the mobile device was previouslycapable of receiving location data; a quality of stored historicalpositioning measurements, estimated locations, and reference locationsthat are available for the mobile device; a quality of service requiredby a requesting location-based service; and a cost associated with usinga certain location estimation method.
 9. The method of claim 1, whereinat least one of the location estimations utilizes a location estimationmethod selected from the group consisting of: TDOA, U-TDOA, OTDOA,IPDL-OTDOA, CI, CI-TA, GPS, AGPS, RTT, CI-RTT, E-OTD, IP Location, WiFIData Base location, Customer provided address location, triangulation,and any combination of the mentioned positioning methods.
 10. The methodof claim 1, wherein the specified reconciliation process identifies asignaling period that should be utilized for one of the initiatedlocation estimations.
 11. The method of claim 1, further comprisingproviding the estimated location of the mobile device to an emergencylocation-based service.
 12. The method of claim 1, further comprisingproviding the estimated location of the mobile device to a non-emergencylocation-based service.
 13. The method of claim 1, wherein the two ormore overlapping access networks are operated by two or more networkoperators.
 14. The method of claim 1, further comprising storing theestimated location of the mobile device.
 15. A location continuitysystem for determining an estimated location of a mobile device that isin range of two or more overlapping access networks, the systemcomprising: a selection module that specifies a reconciliation processfor a mobile device that is in range of two or more overlapping accessnetworks, wherein the mobile device is capable of registering with thetwo or more overlapping access networks and obtaining location data fromthe two or more overlapping access networks; a request module thatinitiates, in accordance with the specified reconciliation process,location estimations of the mobile device in at least two of theoverlapping access networks; and an analysis module that receives,during a time window, one or more sets of location data for the mobiledevice from the two or more overlapping access networks, and determines,in accordance with the specified reconciliation process, an estimatedlocation of the mobile device using the one or more received sets oflocation data.
 16. The system of claim 15, wherein the reconciliationprocess indicates how the location estimation methods should beinitiated in the two or more overlapping access networks.
 17. The systemof claim 15, wherein the reconciliation process provides rules forselecting between received sets of location data if two or more sets oflocation data are received from the indicated location estimationmethods.
 18. The system of claim 17, wherein the rules for selectingbetween received sets of location data specify an accuracy to beachieved by an indicated location estimation method.
 19. The system ofclaim 18, wherein the rules for selecting between the received sets oflocation data further specify selecting the most accurate set oflocation data.
 20. The system of claim 17, wherein the rules forselecting between received sets of location data specify a time to fixto be achieved by an indicated location estimation method.
 21. Thesystem of claim 17, wherein the rules for selecting between receivedsets of location data specify a rank ordering of the two or morelocation estimation methods.
 22. The system of claim 15, wherein theselection module specifies the reconciliation process by analyzing oneor more criteria selected from the group consisting of: characteristicsof the mobile device; an identity of access networks from which themobile device is currently capable of receiving location data; anidentity of access networks from which the mobile device was previouslycapable of receiving location data; a quality of stored historicalpositioning measurements, estimated locations, and reference locationsthat are available for the mobile device; a quality of service requiredby a requesting location-based service; and a cost associated with usinga certain location estimation method.
 23. The system of claim 15,wherein at least one of the location estimations utilizes a locationestimation method selected from the group consisting of: TDOA, U-TDOA,OTDOA, IPDL-OTDOA, CI, CI-TA, GPS, A-GPS, RTT, CI-RTT, E-OTD, IPLocation, WiFI Data Base location, customer provided address location,triangulation and any combination of the mentioned positioning methods.24. The system of claim 15, wherein the specified reconciliation processidentifies a signaling period that should be utilized for one of theinitiated location estimations.
 25. The system of claim 15, wherein theanalysis module further provides the estimated location of the mobiledevice to an emergency location-based service.
 26. The system of claim15, wherein the analysis module further provides the estimated locationof the mobile device to a non-emergency location-based service.
 27. Thesystem of claim 15, wherein the two or more overlapping access networksare operated by two or more network operators.
 28. The system of claim15, wherein the analysis module further stores the estimated location ofthe mobile device.
 29. A method for providing improved locationcontinuity for a mobile device that roams from a home communicationssystem to a visited communications system, the method comprising: inresponse to a request from a location-based service, requesting alocation of a mobile device that is accessing a home communicationssystem; receiving location data generated by one or more home accessnetworks associated with the home communications system; generating anestimated location of a mobile device using the received location data;storing the estimated location of the mobile device; receiving anotification that the mobile device has roamed into a visited accessnetwork associated with a visited communications system; and in responseto a request for the location of the mobile device, transmitting to thevisited communications system the stored estimated location of themobile device determined by the home communications system.
 30. Themethod of claim 29, further comprising storing the received locationdata generated by the one or more home access networks.
 31. The methodof claim 30, further comprising transmitting to the visitedcommunications system the stored location data generated by the one ormore home access networks.
 32. The method of claim 29, furthercomprising: querying the visited communications system for location dataregarding the mobile device; receiving location data from the visitedcommunications system in response to the query; and determining arevised location of the mobile device using the stored location datareceived from the home communications system and the location datareceived from the visited communications system.
 33. The method of claim32, further comprising: receiving an indication of the type of visitedaccess network into which the mobile device has roamed; and based on thereceived indication, specifying a reconciliation policy that determineshow the stored location data received from the home communicationssystem and the location data received from the visited communicationssystem are utilized to determine the revised location of the mobiledevice.
 34. The method of claim 29, further comprising providing thestored estimated location of the mobile device to an emergencylocation-based service.
 35. The method of claim 29, further comprisingproviding the stored estimated location of the mobile device to anon-emergency location-based service.
 36. A location continuity servicefor providing improved location continuity for a mobile device thatroams from a home communications system to a visited communicationssystem, the location continuity service comprising: a request modulethat, in response to a request from a location-based service, requests alocation of a mobile device that is accessing a home communicationssystem; an analysis module that: receives location data generated by oneor more home access networks associated with the home communicationssystem; generates an estimated location of a mobile device using thereceived location data; and stores the estimated location of the mobiledevice; and a database management module that, in response to anotification that the mobile device has roamed into a visited accessnetwork associated with a visited communications system, transmits thestored estimated location of the mobile device to a location continuityservice associated with the visited communications system.
 37. Thesystem of claim 36, wherein the analysis module further stores thereceived location data generated by the one or more home accessnetworks.
 38. The system of claim 37, wherein the analysis modulefurther transmits to the location continuity service associated withvisited communications system the stored location data generated by theone or more home access networks.
 39. The system of claim 36, whereinthe request module further queries the visited communications system forlocation data regarding the mobile device, and wherein the analysismodule further: receives location data from the visited communicationssystem in response to the query; and determines a revised location ofthe mobile device using the stored location data received from the homecommunications system and the location data received from the visitedcommunications system.
 40. The system of claim 39, wherein the analysismodule further: receives an indication of the type of visited accessnetwork into which the mobile device has roamed; and based on thereceived indication, specifies a reconciliation policy that determineshow the stored location data received from the home communicationssystem and the location data received from the visited communicationssystem are utilized to determine the revised location of the mobiledevice.
 41. The system of claim 36, wherein the database managementmodule further provides the stored estimated location of the mobiledevice to an emergency location-based service.
 42. The system of claim36, wherein the database management module further provides the storedestimated location of the mobile device to a non-emergencylocation-based service.
 43. A method for providing improved locationcontinuity for a mobile device that roams from a visited communicationssystem to a home communications system, the method comprising: receivinga request from a location-based service for location informationrelating to a mobile device that has returned to a home access networkin a home communications system after roaming within a visited accessnetwork in a visited communications system; requesting location datarelated to the mobile device from the visited communications system;requesting location data related to the mobile device from the homecommunications system; receiving a first set of location data related tothe mobile device from the visited communications system; receiving asecond set of location data related to the mobile device from one ormore home access networks in the home communications system; andestimating the location of the mobile device using the first set oflocation data and the second set of location data.
 44. The method ofclaim 43, further comprising: receiving information about the type ofvisited access network within which the mobile device roamed; and usingthe received information to determine how the first set of location datashould be utilized with the second set of location data to estimate thelocation of the mobile device.
 45. The method of claim 43, furthercomprising providing the estimated location of the mobile device to anemergency location-based service.
 46. The method of claim 43, furthercomprising providing the estimated location of the mobile device to anon-emergency location-based service.
 47. The method of claim 43,further comprising providing to a location-based service an estimatedlocation of the mobile device based on the first set of location datareceived from the visited communications system, prior to receiving thesecond set of location data from one or more home access networks.
 48. Asystem for providing improved location continuity for a mobile devicethat roams from a visited communications system to a home communicationssystem, the system comprising: a request module that receives a requestfrom a location-based service for location information relating to amobile device that has returned to a home access network in a homecommunications system after roaming within a visited access network in avisited communications system, and, in response to the received request,requests location data related to the mobile device from the visitedcommunications system and from the home communications system; and ananalysis module that: receives a first set of location data related tothe mobile device from the visited communications system and a secondset of location data related to the mobile device from one or more homeaccess networks in the home communications system; and estimates thelocation of the mobile device using the first set of location data andthe second set of location data.
 49. The system of claim 48, wherein theanalysis module further: receives information about the type of visitedaccess network within which the mobile device roamed; and uses thereceived information to determine how the first set of location datashould be utilized with the second set of location data to estimate thelocation of the mobile device.
 50. The system of claim 48, furthercomprising a database management module that provides the estimatedlocation of the mobile device to an emergency location-based service.51. The method of claim 48, further comprising a database managementmodule that provides the estimated location of the mobile device to anon-emergency location-based service.
 52. The method of claim 48,further comprising a database management module that provides to alocation-based service an estimated location of the mobile device basedon the first set of location data received from the visitedcommunications system, prior to receiving the second set of locationdata from one or more home access networks.